For a no confidence vote to be triggered, 48 letters from Conservative MPs must be submitted to the party's chairman and some have claimed that that threshold could soon be reached.

Brexit supporter Andrew Bridgen told The Mail on Sunday that Mrs May must attend Wednesday's meeting of the Tory 1922 committee of backbenchers or risk making "the letters go in even faster".

He said: "This week Theresa May will find that she is drinking in the last chance saloon and the bad news for her is that the bar is already dry."

David Davis, a possible successor to Mrs May, wrote in The Mail on Sunday that the prime minister had "managed to anger not just Leavers but ardent Remainers as well".

He said that the EU has plenty to lose if the UK crashes out of the bloc without a deal in March, adding: "We should not allow ourselves to be bullied by the EU."

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Video:What is Theresa May's Chequers proposal?

A number of anonymous MPs have been quoted as using stark language to describe the PM's predicament - with one saying she is in a killing zone and another saying Mrs May should "bring her own noose" to a meeting with backbenchers.

Brexit minister Suella Braverman declined to condemn such comments, but stressed the Tories should try to stick together.

She told Sky's Sophy Ridge on Sunday: "Colleagues are free to express themselves in the way they wish, but I am very clear that our party is stronger when it's united."

But Robert Halfon, a former minister, told the same programme: "I say to the people giving those quotes, this is not the way to change things."

He said the Tories had a "serious image problem" and warned voters only associate the party with austerity or Brexit.